Field of the Invention
The present invention relates to a display device, and more particularly, to a reflective display device.
Discussion of the Related Art
Recently, with the advancement of the information age, display fields for processing and displaying a large amount of information have been rapidly developed. In response to this trend, various display devices have been introduced and spotlighted. The display devices include liquid crystal display (LCD) devices, plasma display panel (PDP) devices, field emission display (FED) devices, electroluminescence display (ELD) devices and organic light emitting display (OLED) devices.
Recently, the display devices have had properties of a thin profile, a light weight, and low power consumption, whereby application fields of the display devices have been continuously increased. Particularly, the display device has been used as one of the user interfaces in most of electronic devices and mobile devices.
Also, recently, a reflective display device including a reflective area and a display area has been actively studied. A reflective display device may be used as a mirror by reflecting light when an image is not displayed and serves as a general display device when an image is displayed.
According to a related art, however, a related art reflective display device does not control reflectance and a contrast ratio is low because high reflectance is always maintained even when an image is displayed. Thus, the reflective display device cannot be properly operated as a display device.
FIG. 1 is a plane view illustrating one pixel structure of a related art reflective display device that includes a top emission type organic light emitting diode, and FIG. 2 is a cross-sectional view taken along line I-I′ shown in FIG. 1.
Referring to FIGS. 1 and 2, the related art reflective display device includes a display area and a reflective area.
A thin film transistor T is formed on the display area, wherein the thin film transistor T includes a first substrate 10, an active layer 11, a gate insulator 12, a gate electrode 13, an interlayer dielectric 14, a source electrode 15, and a drain electrode 16, and a passivation layer 20 and a planarization layer 30 are formed on the thin film transistor T in due order.
An anode electrode 40 and an auxiliary electrode 50 are formed on the planarization layer 30. The auxiliary electrode serves to reduce resistance of a cathode electrode 80 which will be described later. A bank 60 is formed on the anode electrode 40 and the auxiliary electrode 50 to define a pixel area, an organic light emitting layer 70 is formed in the pixel area defined by the bank 60, and the cathode electrode 80 is formed on the organic light emitting layer 70.
A black matrix 91 and a color filter 92 are formed on a second substrate 90.
A reflective metal 93 is arranged on a reflective area of the second substrate 90. When an image is not displayed on the display area, the reflective metal 93 may serve as a mirror by reflecting light.
However, the reflective metal is maintained at high reflectance even when an image is displayed on the display area, whereby a contrast ratio is lowered and thus the reflective display device cannot be properly operated as a display device.
The related art described above is based on technical information owned by the inventor to derive the present invention or gained through the process of deriving the present invention, and is not necessarily known to the public prior to filing of the application of the present invention.